Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.756.2.28
diff -u -p -r1.756.2.28 common.inc
--- includes/common.inc	8 Oct 2008 20:47:04 -0000	1.756.2.28
+++ includes/common.inc	21 Oct 2008 19:00:55 -0000
@@ -969,7 +969,7 @@ function format_xml_elements($array) {
           $output .= drupal_attributes($value['attributes']);
         }
 
-        if ($value['value'] != '') {
+        if (isset($value['value']) && $value['value'] != '') {
           $output .= '>'. (is_array($value['value']) ? format_xml_elements($value['value']) : check_plain($value['value'])) .'</'. $value['key'] .">\n";
         }
         else {